We are about to sign for an F450 with the new 6.7 and 4.10 gears we also have the option of going with the F550 with 4.88 gears. Both would be with an 11' rugby eliminator dump. Aside from the obvious payload differences my main concern is MPG. I'll say on average our trips are relatively short with mostly rural county road travel. Towing 7-9k almost daily and when hauling it will be on the heavier side of max. Logic tells me that on average we would be better with the 4.10 gears over the 4.88. If anyone has something similar they want to talk about it would be appreciated. Also I would never overload a vehicle on public roads, but hypothetically what is the true max you can throw in an F450 before it becomes a hazard. For example our F250 is rated for 3K payload, it does just fine with 4.5k, but we have gone as high as 6K for very short trips. Of course never on public roads All relative feedback appreciated.